Visual indicating device for electric voltages



F. K. MALSCH 2,749,465

VISUAL. INDICATING DEVICE FOR ELECTRIC VOLTAGES June 5, 1956 Filed Feb. 2, 1951 TOR IN FR/EDR/CH K.

LSCH

BY ZV pg ATTORNEY United Sttes Patent VISUAL INDICATING DEVICE FOR ELECTRIC VOLTAGES Friedrich K. Malsch, Esslingen-Waldenbronn, Germany, assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application February 2, 1951, Serial No. 209,146

Claims priority, application Germany February 28, 1950 3 Claims. (Cl. 313-1075) The known visual indicating devices for electric voltages, especially those used as tuning indicators in radios, make use of an arrangement which consists of a cathode, one or more electrode plates and a somewhat cup-like fluorescent screen which concentrically surrounds the cathode. The deflection plate or plates consist of barlike rods arranged parallel to the cathode. With deflecting rods of this type a maximum shadow sector of approximately 100" is achieved if the deflecting rod is brought to cathode potential. This angle of 100 is, in many cases, insufficient for accurate tuning. Attempts have been made to enlarge the angle by using a deflecting plate instead of a deflecting rod, the plane of which passes thru the cathode axis and the edge of which faces the cathode axis. But the deflection sensitivity achieved with deflecting plates of this type is not much greater than that achieved by the use of deflecting rods. Neither do the electric transverse fields which form between the con trol electrode and the rods generally supporting the screening cap result in a substantial enlargement of the shadow angle. According to the invention counterelectrodes are added to the deflecting organ which are formed and arranged in such a manner that strong and extensive deflecting fields are generated between the potentially variable deflecting electrodes and the counterelectrodes mentioned. For instance, these counterelectrodes, under strong positive potential, usually fluorescent screen potential, consist of plates which lie on a plane thru the cathode axis approximately vertical to that plane which can be erected thru the cathode axis and the deflecting electrode. However the counterelectrodes can also lie in planes which do not pass thru the cathode axis, but which somehow incline thereto in such a manner that they pass thru the plane thru the deflecting electrode and the oathode axis at an angle. The counterelectrode plates can also be partially or completely arched towards the cathode or control electrode. The following examples explain the invention in more detail, reference being had to the drawings in which Fig. 1 is a schematic plan view of a tuning indicator tube according to the present invention;

Fig. 2 is a view similar to Fig. l of a modified embodiment of the present invention;

Fig. 3 is a view taken along the line 33 of Fig. 2; and

Fig. 4 is a side view of the tube of Figs. 2 and 3 partially broken away to disclose in perspective the arrangement of the electrodes.

According to Fig. l counterelectrodes 1 are arranged in such a manner that they run vertically to the deflecting plane. These counterelectrode plates are put under high positive potential, preferably fluorescent screen potential. The counterelectrodes are in close proximity to the cathode 2, so that a strong field between cathode 2 and these counterelectrodes 1 is set up. A grid, under cathode potential or thereabout, can also be arranged in a known manner between the cathode and the other electrodes.

2,749,465 Patented June 5, 1956 Besides this, a strong and extensive field is generated between deflecting electrode 3 and counterelectrodes 1, when the deflecting electrode 3 in relation to fluorescent screen 4 is under a strong negative potential. Cap 5 covers the cathode, the control electrode and the counterelectrodes. By means of this arrangement a substantially larger maximum shadow angle 6 of approximately is achieved. The remaining luminous angle is represented by the shaded area. By means of this arrangement, therefore, a substantial increase in the sensitivity of tuning indicators is obtained. Another advantage of this arrangement is that the deflecting electrode does not have to be any larger than those used in the usual system, so that the stream of electrons from the cathode to the deflecting electrode does not increase either. According to Fig. 2 the counterelectrodes 1 are not placed in a vertical plane to the plane thru the cathode 2 and the control electrode, but inclined towards this plane. This makes the deflecting field between the cathode and counterelectrode still more efifective. Arrangements of this type permit maximum shadow angles 7 of approximately This arrangement is of particular importance for visual indicating devices for electric voltages in which the ray generating system is arranged near the periphery of the tubes. The shadow angle then practically covers the whole fluorescent screen if the deflecting electrode is put under cathode potential. In visual indicating devices of the type described above-with very large maximum shadow anglesthe edges of the luminous sectors are not straight lined without further ado, due to the extensive deflecting fields. However a straight line defining of the sectors is desired, in order to make precise reading possible, especially if a scale or like marking is to be put on the fluorescent screen. According to the invention a straight line defining of the luminous sectors can be achieved by arching the pin like deflecting electrode 10 so that a straight line defining of the luminous sectors will result.

The form of the necessary arch is best found by experimenting, as it is dependent upon the form of the counterelectrode, the distance between the various electrodes as well as the form of the fluorescent screen. Hereby it is of importance to keep the surface of the deflecting electrode as small as possible, in order to keep the controlling current, especially at strong positive deflecting potential nearly screen potential as small as possible. Fig. 3 shows a section of Fig. 2 along line 33. The deflecting rod 10 is arched. It has an oval, prismatic or elliptical cross section. The purpose of this is to reduce the control electrode current.

While I have described above the principles of my invention in connection with visual indicating device for electric voltages it is to be clearly understood, that this description is made only by way of example and not as a limitation to the scope of my invention as Set forth in the objects and in the accompanying claims.

What I claim is:

1. An indicator tube comprising an elongated cathode, a fluorescent screen at least partially surrounding said cathode and adapted to be illuminated by electron bombardment therefrom, an electron deflection electrode mounted on one side of said cathode intermediate the cathode and the screen, a pair of elongated counterelectrodes extending parallel to said cathode adjacent thereto, said counterelectrodes and cathode lying in a plane substantially normal to the plane through said deflection electrode and cathode, said counterelectrodes being plates whose width extends at an angle to the plane through said counterelectrodes and cathode.

2. An indicator tube according to claim 1 wherein the plates forming the counterelectrodes, the cathode and the deflection electrode are all mounted towards the periphcry of the screen on one side of the center of said screen.

3. An indicator tube comprising an elongated cathode, a fluorescent screen at least partially surrounding said cathode and adapted to be illuminated by electron bombardment therefrom, an electron deflection electrode mounted on one side of said cathode intermediate the cathode and the screen, a pair of elongated counterelectrodes extending parallel to said cathode adjacent thereto, said counterelectrodes and cathode lying in a plane substantially normal to the plane through said deflection electrode and cathode, said counterelectrodes, said cath- 4 ode and deflection electrode all being mounted towards the periphery of said fluorescent screen on the same side of the center of said screen.

References Cited in the file of this patent UNITED STATES PATENTS 

